Switch sides within the game
Because of the sun, wind, and perhaps surface conditions, it is required to switch sides within a beach volleyball game. Switches occur when the sum of the scores is a multiple of five, or seven during a rally game to 21 points.
Blocks count as team contact in doubles or triples
As of the 1997-1998 season, this rule was instated in beach volleyball, contrary to the ruling in indoor volleyball. Also, after the first block, any team member may make the second contact, whereas in indoor volleyball, the player who makes first contact cannot make the second contact.
No setting the ball over the net
Because players are more spread out in sand volleyball, setting the ball over the net must be done in such a way that the ball moves perpendicular to the players body. There is no restriction on this action in indoor rules.
Open hand tips and dinks
This is a finesse attack rather than an aggressive attack, and makes for uninteresting outdoor play. Specifically, for doubles, triples and fours, this is disallowed because of the frequency with which it would be used to win a point. We want things interesting, you know?
No center line
Crossing underneath the net is legitimate in beach volleyball, provided the player doing it does not interfere with an opponent.
Perhaps inconsequential in the bigger picture, but interesting just the same, outdoor volleyball pressure is to be between 2.5 and 3.2 pounds per square inch. Indoor ball pressure is between 4.3 and 4.6 pound per square inch.